Characteristics of Polyaniline/Si Heterojunction Solar Cell By Electrochemical Dye Sensitization

Using the electrochemical polymerization dye sensitization （ECDS） method, polyaniline （PAn）, which is used as top region material in solar cells, is sensitized with direct blue dye（DS）, and sensitized Al grid/DS-PAn/n-Si/Al heterojunction solar cells is prepared by ECDS. Influences of the ECDS on the absorption spectrum and the junction characteristics of the solar cell were discussed, and the output characteristics were measured. The results show that the absorption spectrum of the sensitized PAn films is much wider and stronger in Vis-range; the diode quality factor is about 6.3 and the height of latent barrier potential of p-n junction is 0.89 eV; the short-circuit current and the conversion efficiency of sensitized DS- PAn/Si heterojunction solar cells are greatly improved, which the short-circuit current can increase 6 times, the fill factor is 57% and the efficiency can reach 1.42 % under the illumination of 37.2 W/m^2 , respectively.     

Nano-Al2O3/PANI composites with high negative permittivity

Polyaniline (PANI) composites filled with ferroferric oxide and barium titanate were discovered to have metamaterial characteristics in recent years. In this paper, based on micron-Al₂O₃/PANI composites with negative permittivity, the dielectric properties of nano-Al₂O₃/PANI composites were studied. Nano-Al₂O₃/PANI composites had negative permittivity, which was considerably higher than that of PANI and micron-Al₂O₃/PANI composites. The higher negative permittivity was caused by the better dispersibility of nano-Al₂O₃, resulting in the enlargement of polarization voltage on a greater range of PANI molecular chain. Moreover, nano-Al₂O₃/PANI composite with 5 wt% nano-Al₂O₃ has the largest negative permittivity (−2.24 × 10⁶) that has not been reported so far in oxide/PANI composites.     

Morphology and conductivity of polyaniline sub-micron fibers prepared by electrospinning

Sub-micron fibers of pure polyaniline (PANI) doped with sulfuric acid or hydrochloric acid were prepared by electrospinning PANI with suitable molecular weight dissolved in hot sulfuric acid. A modified electrospinning setup was employed with a coagulation bath as a collector, where dilute sulfuric acid was used as coagulation bath. The factors influencing the morphology and conductivity of the synthesized PANI fibers were investigated, including the concentration of dilute H₂SO₄ solution in the coagulation bath, the doped PANI concentration in H₂SO₄ solution, the type of doping acid and the voltage applied to the solution. The morphologies of doped PANI fibers were characterized by scanning electron microscope (SEM). The structure of the resulting fibers was analyzed by Fourier transform infrared spectroscopy and UV–vis spectrometer. The conductivity of PANI fibers were characterized by I–V characteristics. Homogeneous PANI fibers with a diameter of 370 nm and a high conductivity of 52.9 S/cm were prepared. The possible mechanisms of different morphology formation and conductivity of PANI fibers were also discussed.     

Amperometric ascorbate sensor based on conducting polymer: Poly(N-methylaniline) versus polyaniline

Electrocatalytic oxidation of ascorbate (vitamin C) at poly(N-methylaniline) modified electrode has been studied and compared with that proceeding at polyaniline modified sensor. A sigmoid-shaped anodic current transient as a response to addition of ascorbate was found for polyaniline modified electrode in pH-neutral solution, whereas a ‘normal-shaped’ current transient was found to be characteristic for poly(N-methylaniline) modified electrode. Based on this, a hypothesis on the autocatalytic mechanism for electrochemical oxidation of ascorbate was confirmed. It has been shown that poly(N-methylaniline) modified electrode can be used as an amperometric ascorbate sensor, operating in slightly acidic or pH-neutral buffer solutions at a controlled potential of 0.1-0.5 V versus Ag/AgCl, and the dependencies of current response on ascorbate concentration, the thickness of a polymer layer, and operating potential have been analyzed.     

Deposition-order-dependent polyelectrochromic and redox behaviors of the polyaniline-prussian blue bilayer

This study thoroughly compared polyaniline (PANI)/prussian blue (PB) and PB/PANI bilayers with component films by electrochromic photographs, cyclic voltammograms, in situ transmittance spectra, in situ EQCM data and SEM pictures. It was found that both the electrochromic and redox behaviors of a PANI/PB bilayer strongly depended on which layer was deposited first. All of the experimental evidences disclosed that the inner PANI-outer PB bilayer would be superior to the inner PB-outer PANI arrangement and would display better synergistic effects, including better polyelectrochromism (colorless, light green, green/blue and deep blue) and higher redox activity and reversibility. It was also discovered by SEM that subsequent deposition of a PB film with submicron-crack openings on PANI yielded an ideal two-layer structure, but a non-idea bilayer that lacked an obvious boundary between PANI and PB layers was formed when PB was deposited first. In addition, the complex bilayer redox mechanism accompanied by a combinative K⁺, Cl⁻ and H⁺ doping process was studied quantitatively by in situ mass flux analysis and differential transmittance-potential curves. To sum up, this work has demonstrated a simple method to prepare a polyelectrochromic bilayer and provided various useful approaches to characterize bilayer electrodes, especially for those composed of a conducting polymer and a PB analogue.     

Electrical and structural properties of polyaniline/cellulose triacetate blend films

Polyaniline (PANI) has been blended with cellulose triacetate (CTA) to obtain both good mechanical properties and good electrical properties. The effects of PANI weight percentage on the optical, structural, morphological and electrical properties in the blend films of polyaniline and cellulose triacetate (PANI/CTA) have been investigated. The phenomenon of percolation was observed in these blend films. It is found that the electrical conductivity of the blend films increases with the increase of polyaniline content up to a value of 10⁻⁴ S cm⁻¹ at 84 weight percentage of PANI. The experimental percolation threshold of the dried blend films is obtained at 9.5 wt% of polyaniline. The values of Mott’s temperature, density of states at the Fermi level [N (E _f)], hopping distance (R _hop), and barrier height (W _hop) for PANI/CTA blend films are calculated. By applying Mott’s theory, it is found that the PANI/CTA blend films obey the three dimensional variable range hopping mechanism.     

Preparation of polyaniline nanowire arrayed electrodes for electrochemical supercapacitors

Polyaniline (PANI) nanowire arrayed electrodes were successfully synthesized by means of anodic deposition technique using the membrane-template synthesis route. The desired three-dimensional architecture of PANI nanowire arrayed electrodes was characterized with field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) techniques. It was found that the co-deposition nanowires were regular size and continuous with an average diameter of about 30 nm, and the nanowires have an amorphous nature. The electrochemical characterization was performed in 2 M H₂SO₄ aqueous solution. The capacitance of the PANI nanowire arrayed electrode at a charge–discharge current density of 5 Ag⁻¹ is 1142 Fg⁻¹. The nanowire arrayed electrodes showed an excellent capacitive ability for the facility of electrolyte penetration, the ease of proton exchange/diffusion and the metallic conductivity of PANI nanowire arrayed electrodes.     

Studies on one-dimensional polyaniline (PANI) nanostructures and the morphological evolution

In this context, we studied the morphologies and morphology evolution of one-dimensional polyaniline (PANI) nanostructures during a wet chemical oxidation process via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis methods. The results showed that the one-dimensional nanostructures of PANI followed a nucleation, agglomeration or self-growing processes, sequentially. Two distinctive morphologies were observed. One was that cylindrical nanotubes derived, most probably, from the self growing of the as-formed bubble-like ribbons. Another one, in comparison, was rectangular nanotubing structures stemmed from, apparently, a self-guided agglomerating or aggregating process of the as-formed primary nanoparticles, as confirmed unambiguously by both SEM and TEM observations. While the diameters of either individual or hyperbranched PANI nanotubes having a smooth surface were in the range of 250–1500 nm, the size of the rectangular nanotubings was ca. 600 nm.     

Conducting polyaniline composite: From syntheses in waterborne systems to chemical sensor devices

The development of a conducting composite from its one-step synthesis in aqueous dispersed medium to the characterization of its chemical sensor performance is detailed. Composite films of polyaniline and polyacrylate were processed from the crude dispersion with no need for post-formulation. The synthesis has been optimized to be as simple, cheap and transferable as possible. The composite composition is tunable, i.e. the nature of the dopant was varied and its effect on kinetic parameters was observed. Ab initio calculations have been performed on a series of six ionic systems to gain a deeper insight into the contribution of both the stability of the anilinium salts in the composite polymerization. The conductivities of all composites were recorded from room temperature to 150 °C and the thermal stability versus dopant highlighted. The conducting films were then studied as active layers in a chemical sensor. The results showed that these composites, easily synthesized and processed, are ammonia sensitive and exhibit a fast response when exposed to air pollution.